linux-kernel - Re: [PATCH v5 7/8] cpufreq: amd-pstate: enable shared memory type CPPC by default

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Date: Fri, 21 Jun 2024 13:59:53 +0530
From: Gautham R.Shenoy <gautham.shenoy@....com>
To: Perry Yuan <perry.yuan@....com>, <Mario.Limonciello@....com>
CC: <rafael.j.wysocki@...el.com>, <viresh.kumar@...aro.org>,
	<Alexander.Deucher@....com>, <Xinmei.Huang@....com>, <Xiaojian.Du@....com>,
	<Li.Meng@....com>, <linux-pm@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 7/8] cpufreq: amd-pstate: enable shared memory type
 CPPC by default

Perry Yuan <perry.yuan@....com> writes:

> The amd-pstate-epp driver has been implemented and resolves the
> performance drop issue seen in passive mode for shared memory type
> CPPC systems. Users who enable the active mode driver will not
> experience a performance drop compared to the passive mode driver.
> Therefore, the EPP driver should be loaded by default for shared
> memory type CPPC system to get better performance.
>
> Signed-off-by: Perry Yuan <perry.yuan@....com>
> Reviewed-by: Mario Limonciello <mario.limonciello@....com>

Reviewed-by: Gautham R. Shenoy <gautham.shenoy@....com>

> ---
>  drivers/cpufreq/amd-pstate.c | 13 +------------
>  1 file changed, 1 insertion(+), 12 deletions(-)
>
> diff --git a/drivers/cpufreq/amd-pstate.c b/drivers/cpufreq/amd-pstate.c
> index cb750ef305fe..0f8ffbc0dc2a 100644
> --- a/drivers/cpufreq/amd-pstate.c
> +++ b/drivers/cpufreq/amd-pstate.c
> @@ -86,15 +86,6 @@ struct quirk_entry {
>  	u32 lowest_freq;
>  };
>  
> -/*
> - * TODO: We need more time to fine tune processors with shared memory solution
> - * with community together.
> - *
> - * There are some performance drops on the CPU benchmarks which reports from
> - * Suse. We are co-working with them to fine tune the shared memory solution. So
> - * we disable it by default to go acpi-cpufreq on these processors and add a
> - * module parameter to be able to enable it manually for debugging.
> - */
>  static struct cpufreq_driver *current_pstate_driver;
>  static struct cpufreq_driver amd_pstate_driver;
>  static struct cpufreq_driver amd_pstate_epp_driver;
> @@ -1815,11 +1806,9 @@ static int __init amd_pstate_init(void)
>  		/* Disable on the following configs by default:
>  		 * 1. Undefined platforms
>  		 * 2. Server platforms
> -		 * 3. Shared memory designs
>  		 */
>  		if (amd_pstate_acpi_pm_profile_undefined() ||
> -		    amd_pstate_acpi_pm_profile_server() ||
> -		    !cpu_feature_enabled(X86_FEATURE_CPPC)) {
> +		    amd_pstate_acpi_pm_profile_server()) {
>  			pr_info("driver load is disabled, boot with specific mode to enable this\n");
>  			return -ENODEV;
>  		}
> -- 
> 2.34.1